1. Technical Field
The present invention relates to a radio frequency (RF) power amplifier, in particular, to a RF power amplifier for increasing a power added efficiency and a linearity.
2. Description of Related Art
Different specifications for the power transmitters in communication systems are needed because there are many methods for modulating signals. In recent years, an orthogonal frequency-division multiplexing (OFDM) modulated signal has been used in wireless communication networks (e.g., the communication network suitable for IEEE 802.11a/b/g specification) which is similar to a modulated method of Amplitude Modulation (AM). Therefore, it needs a high-linearity power amplifier. In general, high-linearity power amplifiers use common source (CS) power amplifiers of Class A or Class AB to increase the linearity. To increase the communication quality, it is essential to further increase the linearity and the power added efficiency of the power amplifier.